Appendix C — Configuration Memory Address Space Map

OpenLCB defines a set of well-known address spaces accessed via the Memory Configuration Protocol (datagrams). Each space has an 8-bit identifier and contains a specific type of data. This appendix documents all address spaces supported by the library.

C.1 Address Space Summary

C.2 ACDI Manufacturer Space Layout (0xFC)

The ACDI Manufacturer space provides read-only access to the same identification strings reported via SNIP:

C.3 ACDI User Space Layout (0xFB)

The ACDI User space provides read/write access to user-assignable identification strings:

C.4 Address Space in node_parameters_t

Each address space has a corresponding user_address_space_info_t entry in node_parameters_t that describes its properties:

typedef struct {
    bool present : 1;           // Space exists on this node
    bool read_only : 1;         // Space is read-only
    bool low_address_valid : 1; // low_address field is meaningful
    uint8_t address_space;      // Space identifier (0x00-0xFF)
    uint32_t highest_address;   // Highest valid address in space
    uint32_t low_address;       // Lowest valid address (if low_address_valid)
    char description[59];       // Human-readable description
} user_address_space_info_t;

The node_parameters_t structure contains one entry for each well-known space:

C.5 Command Encoding

Configuration memory commands use the datagram protocol. The first byte of the datagram payload is always 0x20 (CONFIG_MEM_CONFIGURATION), and the second byte is the command code. The address space is encoded either in the command byte itself (for spaces 0xFD-0xFF) or in byte 6 of the payload: